The present invention relates to a self-diagnosis system for a motor vehicle.
Recently, a motor vehicle has been equipped with an electronic control system for controlling various components of an engine, such as fuel injectors, thereby improving driveability, exhaust gas emission, fuel consumption, and engine power. The electronic control system controls the components based on information represented by output signals from various sensors for detecting engine operating conditions. Accordingly, if malfunctions of components and sensors occur, the engine does not properly operate.
However, because of the complexity of the electronic control system, it is difficult to immediately find out the trouble. Accordingly, a self-diagnosis device for easily checking the electronic control system should be provided in the motor vehicle.
Japanese Patent Application Laid Open 59-24270 discloses an electronic control system provided with the self-diagnosis system where signaling lamps provided on the vehicle are lit or flashed to indicate a trouble code representing a defective part in the control system when abnormalities occur in sensors and actuators such as injectors. Data of the troubles are written in a backup random-access memory (RAM) at a predetermined address, which is provided in the electronic control system. A diagnostician in an auto shop reads out the trouble code indicated by lamps or a display of a computer which is connected to the vehicle. Thus, information on the trouble is recognized by the diagnostician so that the defective parts such as sensors and switches can be appropriately repaired.
However, in the conventional diagnosis system, an abnormality which occurs only under a particular driving condition which can not reoccur in the auto shop can not be diagnosed in the shop. Thus, the repair is troublesome and in some cases, the cause of the abnormality cannot be thoroughly explained.